The proposed experiments are designed to analyze by the ablation method the contribution of certain brain structures to visual perception in monkeys. More specifically, the role of the superior colliculus, pulvinar, and of extrastriate cortical areas in orientation, localization and discrimination learning will be investigated by observing the visually-guided behavior of monkeys in visual learning situations and by recording eye movements before and after selective surgical removal of these structures. Another related problem to be investigated is whether visual information necessary for the performance of color and form discriminations may be conveyed to extrastriate visual areas independently of the geniculostriate system. The experiments are relevant to recently developed concepts of a mammalian tecto-thalamic pathway, which may provide inputs into extratriate cortical areas, and the findings may provide information concerning the role of the tectum and this pathway in primate vision.